How Do Release Days Work?

Sorry if this is a dumb question but how early are cards stocked? For example, Walmart opens at 6 and Target opens at 7. If I showed up right as they open can I expect stuff to be available or does it take a little while for someone to come stock the shelves?

Not a scalper or anything - just wanted to figure out what my game plan is before I waste a ton of time and gas lol. I’ve never really tried finding product Day 1 of a new set. Thanks 🙃